We propose that genetic variation in lysosomal lipases, phospholipases, and diesterases may cause uncharacterized lysosomal storage diseases and may be related to the pathogenesis of atherosclerosis. We have established assay conditions for acid lipase using triglyceride and cholesterol ester substrates and will extend this to include monoglyceride and diglyceride substrates. We have demonstrated successfully the feasibility of assaying phospholipases in extracts of cultured human fibroblasts. Phospholipases A1, A2, C, and D will be assayed by incubation of radioactive phospholipids followed by thin layer chromatography of products, autoradiography, and scintillation counting of radioactive spots. We will measure phospholipase activities in fibroblasts from control, Wolman, cholesterol ester storage disease, Niemann-Pick, and other patients. We will perform enzyme purification for acid lipase and selected phospholipases. Measurement of multiple lipase and phospholipase activities on column fractions from enzyme purification will combine with data from mutant cells to further clarify the number of enzymes and genetic loci involved and the specific hydrolytic capacities of each enzyme. We also propose to measure glycerophosphorylcholine diesterase activity as an important unstudied lysosomal function. We will measure phospholipase and diesterase activities in fibroblasts from patients with disorders such as neuronal ceroid lipofuscinosis, sea blue histiocyte disease, "cephalin lipidosis", neuroaxonal dystrophy, and from undiagnosed patients with clinical features of a lysosomal storage disease. Acid lipase will be assayed in lymphocytes of patients undergoing coronary arteriography in an attempt to demonstrate if genetic variation in this enzyme is important in the pathogenesis of atherosclerosis.